1. Field of the invention
The present invention relates to a bumper structure for a vehicle and more particularly to a bumper structure capable of securing safety of a pedestrian when the vehicle traveling at low speeds contacts the pedestrian.
2. Description of the Related Art
In recent years, automobile bumpers capable of minimizing the damage to a pedestrian when a vehicle traveling at low speeds contacts the pedestrian, have been proposed.
An example of such bumpers is disclosed in Japanese Patent Application Laid-open No. Toku-Kai-Hei 11-78732. FIG. 7 is an exploded perspective view of the example of the a bumper 101. The bumper includes an upper bumper beam 102 and a lower bumper beam 103 extending in a widthwise direction of a vehicle and covered at the front surface thereof with a soft-plastic-made bumper face. The upper bumper beam 102 and the lower bumper beam 103 are supported through an upper bumper stay 104 and a lower bumper stay 105 by a radiator panel 106, respectively.
The upper bumper stay 104 comprises a long outer stay 107 and a short inner stay 108 fitted to the 107. The outer stay 107 is connected at the front end thereof with the upper bumper beam 102 and is connected at the rear end thereof with the radiator panel 106. On the other hand, the inner stay 108 is connected at the rear end thereof only with the radiator panel 106. The outer stay 107 is constituted by a front stay 107a broadening toward the front end and having a relatively high strength and a rear stay 107b having a relatively low strength.
Further, the lower bumper stay 105 is connected at the front end thereof with the lower bumper beam 103 and is connected at the rear end thereof with the radiator panel 106 through a bracket (not shown). The longitudinal strength of the upper bumper stay 104 is established to be smaller than that of the lower bumper stay 105.
According to the bumper structure described above, as shown in FIGS. 8 and 9, when a vehicle traveling at low speeds contacts a pedestrian M, the upper bumper beam 102 contacts a leg R in the vicinity of a knee H of the pedestrian M and the lower bumper beam 103 contacts a lower portion of the leg R.
Then, the upper bumper stay 104 supporting the upper bumper beam 102 collapses at the rear stay 107b and the lower bumper stay 105 collapses itself. Since the strength of the upper bumper stay 104 is smaller than that of the lower bumper stay 105, the amount of deformation of the upper bumper stay 104 is larger than that of the lower bumper stay 105. As a result, as shown in FIG. 9, a force rotating the leg R in the direction A that is, a force scooping the leg R upward is applied to the leg R. This force exerted on the leg R acts as reducing a bending angle xcex8 generating in the knee H. Thus, the damage causing to the knee H can be alleviated by properly controlling the behavior of the leg R at collisions.
When a large impact is applied, both of the front stay 107b having a larger strength and the inner stay 108 collapse.
The bumper structure according to Toku-Kai-Hei 11-78732, when vehicles running at low speeds contact pedestrians, provides the protection of their legs, particularly knees easily being subjected to damages.
However, in this bumper structure, depending on where a pedestrian contacts the automobile bumper, the behavior of the leg R sometimes can not be controlled properly. That is, since the upper bumper stay 104 and the lower bumper stay 105 are disposed on the left and right sides of the vehicle, respectively, for example, when the pedestrian contacts the bumper beams 102 and 103 in the vicinity of the upper bumper stay 104 and the lower bumper stay 105, the rear stay 107b and the lower bumper stay 105 collapse as expected. However, in case where the pedestrian M collides with the middle portion of the upper bumper beam 102 and the lower bumper beam 103, an impact load is dispersed into the left and right bumper stays 104, 105 and as a result, the rear stay 107b and the lower bumper stay 105 provide small collapses and inadequate deformations.
Further, there is fear that the reduction of strength of the upper bumper stay 104 weakens a holding rigidity of the upper bumper beam 102 and as a result, when a large impact load is applied, such bumper structure presents a poor performance as an automobile bumper.
It is an object of the present invention to provide a bumper structure having an adequate performance as an automobile bumper and at the same time capable of reducing damages to knees of pedestrians.
To achieve the object, a bumper structure for a vehicle covered with a bumper face on the front side thereof and extending in a widthwise direction of the vehicle, comprises an upper bumper beam extending in a widthwise direction of the vehicle, an upper energy absorbing member provided between the bumper face and the upper bumper beam, a lower bumper beam provided below the upper bumper beam and extending in a widthwise direction of the vehicle and a lower energy absorbing member provided between the bumper face and the lower bumper beam and having a larger strength resisting an impact load in a longitudinal direction of the vehicle than the upper energy absorbing member.